The present invention relates to a resist material suitably used in microprocessing technique for semiconductor devices and a pattern formation method using the same.
Recently, in accordance with the increased degree of integration and the increased operation speed of LSIs, a pattern rule is required to be further refined. The pattern rule has been rapidly refined owing to the increased NA (numerical aperture) of a projection lens, the improved performance of a resist material, the reduced wavelength of exposing light and the like.
Currently, ArF excimer laser (of a wavelength of a 193 nm band) is used as the exposing light for coping with a design rule of 90 nm or less.
Now, a pattern formation method using a conventional resist material will be described with reference to FIGS. 3A through 3D.
First, a positive chemically amplified resist material having the following composition is prepared:
Base polymer: poly((2-methyl-2-adamantyl methacrylate (50 mol %)-γ-butyrolactone methacrylate (40 mol %)-2-hydroxyadamantyl methacrylate (10 mol %)) . . . 2 g.
Acid generator: triphenylsulfonium trifluoromethane sulfonate . . . 0.06 g.
Quencher: triethanolamine . . . 0.002 g.
Solvent: propylene glycol monomethyl ether acetate . . . 20 g.
Next, as shown in FIG. 3A, the chemically amplified resist material is applied on a substrate 1, so as to form a resist film 2 with a thickness of 0.35 μm.
Then, as shown in FIG. 3B, the resist film 2 is subjected to pattern exposure by irradiating with exposing light 4 of ArF excimer laser with NA of 0.85 through a mask 3.
After the pattern exposure, as shown in FIG. 3C, the resist film 2 is baked by using a hot plate at a temperature of 105° C. for 60 seconds. Thereafter, the resultant resist film 2 is developed with a 2.38 wt % tetramethylammonium hydroxide developer. Thus, as shown in FIG. 3D, a resist pattern 2a with a line width of, for example, 0.08 μm made of an unexposed portion of the resist film 2 is obtained.
In the resist pattern 2a obtained by the pattern formation method using the conventional resist material, however, surface roughness and pattern roughness are frequently caused, resulting in degrading its shape (see, for example, G. Lee et al., Proc. SPIE. Vol. 5753, p. 390 (2005)).
When a resist pattern in such a degraded shape is used in etching, a pattern obtained in the etched film is also in a degraded shape, and hence, the productivity and the yield in the fabrication process for semiconductor devices are disadvantageously lowered.